The present invention relates to a process for conveying vehicle bodies through a treatment tank for the surface treatment of the vehicle bodies.
Furthermore, the present invention relates to a conveyor device for conveying vehicle bodies through a treatment tank for the surface treatment of the vehicle bodies, comprising a conveyor which introduces the vehicle bodies into the treatment tank, conveys them through the treatment tank and brings them out of the treatment tank again.
Such a process and such a device are known, for example, from DE 36 12 128 A1. With the process known from this publication, the vehicle bodies mounted on support carriages (designated in the following as skid frames) are suspended on a conveyor line, with which the vehicle bodies are conveyed through a phosphating and painting plant, with the aid of oscillatingly suspended pairs of support elements which are each formed from two L-shaped arms located opposite one another.
The vehicle bodies are immersed in the phosphating and painting bath by the pairs of support elements with the vehicle bodies suspended therefrom being conveyed along an inclined conveyor section of the conveyor line into the relevant treatment tank. In this respect, a floor pan of the respective vehicle body is first immersed in the treatment tank. Since the floor pan of a vehicle body offers the liquid from the treatment tank only small entry cross sections for penetrating into the interior of the vehicle body, a high counterpressure (immersion resistance) must be overcome when the vehicle body is immersed in the treatment tank.
Furthermore, as the vehicle body is emerging from the treatment tank the floor pan of the vehicle body leaves the treatment tank last. In this respect, it is possible that the liquid of the treatment tank will run only incompletely out of the interior of the vehicle body or irritating markings will remain when the liquid runs out after leaving the treatment tank.
Furthermore, a process and a device are known from DE 196 41 048 A1, with which vehicle bodies are immersed in the treatment tank due to superposition of a translatory movement and a rotary movement at the beginning of a treatment tank and at the end of the treatment tank are moved out of the treatment tank by a like superposition of translatory and rotary movements. On account of the superposition of the translatory movement of the vehicle bodies with a rotary movement at the beginning and at the end of the treatment tank, the depth of the treatment tank must be selected to be larger than is required for the process according to DE 36 12 128 A1. Moreover, higher flow velocities of the liquid of the treatment tank result relative to the submerging or emerging vehicle body due to the superposition of the translatory and the rotary movements which leads to a greater mechanical load on the vehicle body and its holder. In particular, holding elements provided on the vehicle body, as a result of which doors, hood and trunk lid or tailgate of the vehicle body are kept in a slightly opened state during the surface treatment, have to be of a more stable design.
The object underlying the present invention is therefore to provide a process of the type specified at the outset, with which the liquid of the treatment tank offers only a slight immersion resistance to the vehicle bodies during immersion and the flow velocities of the liquid of the treatment tank relative to the submerging and emerging vehicle bodies are kept low.
This object is accomplished in accordance with the invention, in a process for conveying vehicle bodies through a treatment tank for the surface treatment of the vehicle bodies, in that prior to their introduction into the treatment tank the vehicle bodies are transferred from a standard position, in which window openings of the respective vehicle body are arranged above the floor pan of the vehicle body, into a headfirst position, in which the window openings of the respective vehicle body are arranged beneath the floor pan of the vehicle body, and that the vehicle bodies are subsequently introduced into the treatment tank, conveyed through the treatment tank and brought out of the treatment tank again in the headfirst position.
As a result of the inventive idea, the immersion resistance offered to the vehicle body during immersion is considerably reduced since the window openings of the vehicle body, which offer the liquid of the treatment tank large entry cross sections for penetrating into the interior of the vehicle body, are immersed in the treatment tank earlier than is the case when the vehicle bodies are introduced in the standard position.
Moreover, no increased flow velocities of the liquid of the treatment tank relative to a submerging or emerging vehicle body occur since the vehicle body is already transferred into the headfirst position before being introduced into the treatment tank. For the same reason the depth of the treatment tank need also not be increased.
When the vehicle bodies are brought out of the treatment tank in the headfirst position, the liquid which has penetrated the interior of the vehicle bodies can run off completely and free from markings through the window openings.
Furthermore, as a result of the fact that during its transport through the treatment tank the roof of the vehicle body hangs downwards no air bubbles or foam can collect underneath the roof, as is frequently the case when a vehicle body is conveyed through a treatment tank in a standard position. On the contrary, such air bubbles and foam can escape upwards out of the interior of the vehicle body through outlet openings in the floor area of the vehicle body when a vehicle body is conveyed through the treatment tank in a headfirst position. As a result, it is possible to avoid parts of the vehicle body not coming into contact with the liquid of the treatment tank on account of air bubbles or the formation of foam and thus not being subjected to the desired treatment, i.e., for example, cleaned, degreased or painted.
Furthermore, when the vehicle bodies are transported through the treatment tank in a headfirst position the roof and the hood hang downwards and so no dirt from the treatment tank can be deposited on these particularly critical, visible surfaces of the vehicle body. As a result, treatment errors, for example, paint errors on account of sedimented dirt particles are avoided, in particular, on the extended, horizontal visible surfaces of the vehicle body.
Finally, the immersion contour of a vehicle body introduced into the treatment tank in a headfirst position differs from the immersion contour of a vehicle body introduced in a standard position which canxe2x80x94as a function of the shape of the vehicle body and the predetermined minimum immersion timexe2x80x94result in the treatment tank of the inventive process being of a shorter design than with a process, with which the vehicle bodies are introduced into the treatment tank in the standard position.
Such a shortening of the treatment tank is possible, in particular, with short immersion times.
Once the vehicle bodies have been brought out of the treatment tank they can be returned to the standard position in order to carry out a further step in the production process of the vehicle, for example, the assembly of additional components on the vehicle body which is normally carried out in the standard position of the vehicle body.
It is, however, in no way necessary to return the vehicle body to the standard position after each passage through a treatment tank. On the contrary, it is possible to convey the vehicle bodies in the headfirst position through several treatment areas arranged one behind the other, for example, pretreatment areas, painting areas and drying areas and not return the vehicle bodies to the standard position until after the last of these treatment sections.
In principle, the orientation of the vehicle body relative to the direction of conveyance in the headfirst position is optional in the inventive process as long as the window openings of the respective vehicle body are arranged beneath the floor pan of the vehicle body.
It may, for example, be provided for the windshield openings of the vehicle bodies to point rearwards in the direction of conveyance in the headfirst position of the vehicle bodies.
A particularly low immersion resistance is, however, achieved when it is advantageously provided for the windshield openings of the vehicle bodies to point forwards in the direction of conveyance in the headfirst position of the vehicle bodies.
In a preferred development of the inventive process, the vehicle bodies are transferred from the standard position into the headfirst position by means of a rotation, preferably by means of a rotation through approximately 180xc2x0.
In principle, such a rotation can take place about any optional horizontal axis of rotation.
It is, however, advantageously provided for the vehicle bodies to be transferred from the standard position into the headfirst position by means of a rotation about an axis of rotation aligned essentially at right angles to the direction of conveyance. With such an orientation of the axis of rotation, the bearing and drive elements required for carrying out the rotation can be arranged to the side next to the path of conveyance of the vehicle bodies without hindering the conveyance of the vehicle bodies along the direction of conveyance.
In principle, it could be provided for the vehicle bodies to be arranged directly on a conveyor which conveys the same through the treatment tank.
However, a development of the inventive process is preferred, with which the vehicle bodies are each arranged on a skid frame.
A xe2x80x9cskid framexe2x80x9d is thereby to be understood as any transport means for a workpiece which comprises at least two skid runners which are arranged at a distance from one another transversely to the direction of transport of the workpieces, wherein each skid runner has a contact surface for supporting the transport means on an essentially flat supporting surface of a roller conveyor.
The skid runners of the skid frame may be mounted directly on the workpiece so that the workpiece itself undertakes the connection of the skid runners with one another.
However, crossbars are customarily provided which are connected to each of the skid runners by supports in order to connect the skid runners of the skid frame rigidly to one another.
The supporting surface of a roller conveyor is defined by the apex lines of the support members of the roller conveyor and corresponds to the common tangential plane of the cylindrical support members of the support rollers of the roller conveyor.
A vehicle body arranged on such a skid frame can thus be conveyed horizontally by means of roller conveyors in a simple manner.
Moreover, in this case suspension and/or entrainment devices, which are required for transporting the vehicle body with other conveyor devices, can be arranged on the skid frame.
It is advantageously provided for the skid frames to be arranged above the vehicle bodies in the headfirst position so that the skid frames can be connected to the floor pan of the respective vehicle body in the customary manner by means of suitable locking elements.
It is particularly favorable when skid frames are used, the skid runners of which each have two contact surfaces facing away from one another for supporting the skid frame on an essentially flat supporting surface of a roller conveyor. This makes it possible to support the skid frame on the supporting surface of a roller conveyor with the contact surface pointing respectively downwards and thus to convey the skid frame horizontally by means of this roller conveyor not only in a first position, in which the vehicle body arranged on the skid frame is in the standard position, but also in a second position, in which the vehicle body arranged on the skid frame is in the headfirst position.
The presence of two differently oriented contact surfaces on the skid runners of the skid frame is also of advantage during the transfer of the vehicle bodies from the standard position into the headfirst position.
It may, in particular, be provided for both contact surfaces of the skid runners to abut on a respective, essentially flat supporting surface of a turning device during the transfer of the vehicle bodies from the standard position into the headfirst position by means of the turning device. As a result, a particularly reliable securing of the skid frame and the vehicle body arranged thereon against any movement at right angles to these supporting surfaces during the transfer from the standard position into the headfirst position is ensured.
In principle, the essentially flat supporting surfaces of the turning device can, for example, be formed by holding-down devices with holding-down surfaces extending tangentially to the respective supporting surface.
It is, however, of advantage when at least one of the supporting surfaces of the turning device is designed as a common tangential plane of the support members of the support rollers of a roller conveyor. In this case, the skid frame with the vehicle body arranged thereon can, for example, be conveyed onto the relevant supporting surface of the turning device by means of this roller conveyor prior to the rotation.
It is particularly favorable when both supporting surfaces of the turning device are each designed as a common tangential plane of the support members of the support rollers of a respective roller conveyor. In this case the skid frame with the vehicle body arranged thereon can be conveyed onto the first supporting surface of the turning device by means of the first of these roller conveyors prior to the rotation and after the rotation can be conveyed by means of the second roller conveyor away from the second supporting surface of the turning device and out of the turning device.
In order to prevent the skid runners of the skid frame from being treated, for example, painted as well in the treatment tank and therefore having to be cleaned after a few passages through the treatment tank, it is advantageously provided for the skid runners of the skid frame to be conveyed over the treatment tank above the level of the treatment tank and thus not to come into contact with the liquid in the treatment tank.
In a preferred development of the inventive process it is provided for the vehicle bodies to be conveyed through the treatment tank suspended on a pendulum conveyor.
It may be provided, in particular, for the vehicle bodies to be suspended in the pendulums of the pendulum conveyor in the headfirst position.
In this case, a customary pendulum conveyor such as that known, for example, from DE 36 12 128 A1 can be used to convey the vehicle bodies through the treatment tank without this pendulum conveyor needing to be provided with any additional means for transferring the vehicle bodies from the standard position into the headfirst position.
The pendulum conveyor to be used can, however, also be adapted to the special features of the inventive process in an advantageous manner.
For example, it is, in particular, of advantage when it is provided for the pendulums of the pendulum conveyor to be arranged completely above the vehicle bodies suspended on the pendulums. In this case, the pendulums of the pendulum conveyor, in contrast to customary pendulum conveyors such as the pendulum conveyor known, for example, from DE 36 12 128 A1, do not engage around the vehicle bodies suspended on the pendulum conveyor and so no additional space need be provided for accommodating the pendulums in the treatment tank to the side next to the vehicle bodies and beneath the vehicle bodies. The width and the depth of the treatment tank can therefore be selected to be smaller than with a customary pendulum conveyor and so the treatment tank can be accommodated in a more space-saving manner and the amount of liquid needed to fill the treatment tank is reduced.
If the treatment tank is an electrophoretic coating bath, a more uniform coating of the vehicle body will be achieved as a result of the fact that the pendulums of the pendulum conveyor are arranged completely above the vehicle bodies suspended on the pendulums since the pendulums, in contrast to customary pendulum conveyors, are not located in the space between the anodes and the body. There is, therefore, no area of the body xe2x80x9cshadedxe2x80x9d by the pendulums, in which the coating has a smaller layer thickness.
Furthermore, it is favorable when the pendulums of the pendulum conveyor are conveyed over the treatment tank above the level of the treatment tank. In this case the pendulums of the pendulum conveyor do not come into contact with the liquid of the treatment tank and are not treated, for example, painted as well and so it is not necessary to clean the pendulums after a few cycles by the pendulum conveyor.
There are numerous possibilities for the design of the pendulum conveyor.
For example, it may be provided for the pendulums of the pendulum conveyor to be conveyed by means of a one-strand conveyor means, wherein the conveyor means can be arranged, for example, centrally above the treatment tank.
Alternatively thereto, it is also possible for the pendulums of the pendulum conveyor to be conveyed by means of a two-strand conveyor means.
In this case, the guideways for the conveyor means can be arranged directly over the treatment tank in order to keep the width of a booth, in which the treatment tank is arranged, as small as possible.
In this case it can, however, also be provided for guideways for the conveyor means to be arranged above the treatment tank and to the side next to it so that abrasion particles generated at the guideways for the conveyor means are prevented from falling downwards into the treatment tank and/or onto the vehicle bodies conveyed through the treatment tank.
In order to protect the conveyor means and the guideways for the conveyor means from contact with aggressive chemical substances from the treatment tank, it is of advantage when each strand of the conveyor means is arranged in a respective closed conveyor means channel.
In order to prevent aggressive chemical substances from penetrating the interior of the conveyor means channel it is favorable when the interior of the conveyor means channel is maintained at an increased air pressure in comparison with the interior of the booth containing the treatment tank.
The treatment tank, through which the vehicle bodies are conveyed in the headfirst position, may, for example, be a cleaning, degreasing, phosphating or painting bath.
When the treatment tank is an electrophoretic painting bath, sill anodes arranged above the path of the vehicle bodies are advantageously used in the treatment tank in order to achieve an adequate coating thickness in the area of the sill panels of the floor pan of the vehicle bodies. Since the vehicle bodies are conveyed through the treatment tank in a headfirst position, the sill anodes may be arranged above the path of the vehicle bodies close to the level of the treatment tank where they are accessible for maintenance purposes without the liquid needing to be drained from the treatment tank.
A further object underlying the present invention is to provide a conveyor device of the type specified at the outset which makes it possible to introduce the vehicle bodies into the treatment tank with low immersion resistance without increased flow velocities of the liquid of the treatment tank relative to the submerging or emerging vehicle bodies occurring.
This object is accomplished in accordance with the invention, in a conveyor device for the surface treatment of vehicle bodies, in that the conveyor device comprises a transfer device which transfers the vehicle bodies prior to their introduction into the treatment tank from a standard position, in which window openings of the respective vehicle body are arranged above the floor pan of the vehicle body, into a headfirst position, in which the window openings of the respective vehicle body are arranged beneath the floor pan of the vehicle body, and that the conveyor of the conveyor device subsequently introduces the vehicle bodies into the treatment tank, conveys them through the treatment tank and brings them out of the treatment tank again in the headfirst position.
Special developments of the inventive conveyor device are provided which correspond to the subject matter of the invention process, the advantages of which have already been discussed above.
A treatment device for the surface treatment of vehicle bodies is also provided which comprises a treatment tank for the surface treatment of the vehicle bodies and an inventive conveyor device for conveying vehicle bodies through the treatment tank.
Additional features and advantages of the invention are the subject matter of the following description and drawings illustrating embodiments.